Adults born around 1990 have twice the risk of colon cancer and four times the risk of rectal cancer compared with those born around 1950.
That’s because, while the incidence of colorectal cancer in the United States is quickly declining among people over age 50, it’s going up among younger adults.
“I think it’s extremely significant,” Dr. Smith, chief of the Spectrum Health Cancer Center, said of the research, which examined colorectal cancer incidence data from 1974 to 2013.
“In the absolute numbers it is small, but the trend is very significant because if it continues, it will be a major shift.”
Dr. Smith said colorectal cancer could become a disease of younger adults.
The trouble is, the medical community doesn’t know why this shift to a younger population is happening.
“We simply don’t know the reasons,” Dr. Smith said, especially when the rates in the over-50 population have come down. She has a theory, though, and it points to America’s obesity trend.
“We know that obesity, inactivity and diabetes are all increasing in incidence in younger individuals. We also know that those are associated with colorectal cancer,” she said. “So it could be that obesity and the related behaviors and diseases are leading to more colorectal cancers at an earlier age.”
Inflammatory bowel disease, another risk factor for colorectal cancer, is also increasing in incidence and may be contributing to the current shift, Dr. Smith said.
The study, sponsored by the American Cancer Society and the National Cancer Institute, concluded that colon cancer incidence rates have increased by as much as 2.4 percent per year since the mid-1980s in adults ages 20 to 39. Rectal cancer rates “have been increasing longer and faster” in the same age group.
These statistics ring true at the Spectrum Health Cancer Center, where the percentage of colorectal cancer patients under age 50 is 10.8 percent and rising—a proportion Dr. Smith said is slightly higher than the norm.
Still, she cautioned that this percentage might not reflect the overall West Michigan population because regional cancer centers like Spectrum Health often care for younger, higher-risk patients, who need the comprehensive array of services the center offers, including medical genetics.
The study’s authors also concluded that America’s obesity epidemic could be behind the rising incidence of colorectal cancer among young people.
Along with more research into the causes of the trend, they called for new strategies to move Americans toward healthier food and more active lifestyles.
Dr. Smith agreed, calling on doctors to teach patients from a young age about the risk factors for cancer and heart disease, which are similar.
“Exercise, healthy diet—eat your fiber, vegetables, fruit, low fat, not a lot of red meat, not a lot of processed foods. All of those things are critically important for health,” she said.
Be your own advocate
So what signs should people, whether younger or older, watch for as possible indicators of colorectal cancer? Dr. Smith pointed to three main symptoms:
- Rectal bleeding or blood in the stool
- Persistent abdominal discomfort, such as cramps, pain or gas
- Change in bowel habits, including diarrhea or constipation that lasts longer than four weeks
Anyone with these symptoms should see their doctor and ask about a colonoscopy, which Dr. Smith calls the gold standard for colorectal cancer screening.
“The best thing about colorectal cancer is that it can be preventable—because if we do a colonoscopy and remove polyps that could eventually turn into cancer, we’ve actually treated the cancer before it occurred,” she said. “And that’s really great.”
The recommended colorectal cancer screening age for individuals without risk factors or symptoms is 50. If the trend revealed in this study continues, Dr. Smith said, professional organizations and the U.S. Preventive Services Task Force may choose to lower the screening age. Today, however, there’s not enough evidence for a change.
If you’re younger than 50 and experiencing symptoms, raise the question of cancer.
“It’s critical that we think about cancer as a possibility,” Dr. Smith said. “You know your body best, and if you feel that something is wrong … make sure that you get an understanding, at least, of what it could or couldn’t be. Talk to your doctor.
“The most important thing is to be your own health advocate.”